Apparatus and method for differentiating between tissue and mechanical obstruction in a surgical instrument

ABSTRACT

A surgical instrument is provided. The surgical instrument includes: a handle assembly; a jaw assembly comprising a staple cartridge containing a plurality of staples and an anvil to form the plurality of staples upon firing; a drive assembly at least partially located within the handle and connected to the jaw assembly and the lockout mechanism; a motor disposed within the handle assembly and operatively coupled to the drive assembly; and a controller operatively coupled to the motor, the controller configured to control supply of electrical current to the motor and to monitor a current draw of the motor, wherein the controller is further configured to terminate the supply of electrical current to the motor in response to a rate of change of the current draw indicative of a mechanical limit of at least one of the jaw assembly, the drive assembly, or the motor.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to a U.S.Provisional Patent Application Ser. No. 61/879,445, filed on Sep. 18,2013, the entire contents of which are incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to surgical apparatuses, devices and/orsystems for performing endoscopic surgical procedures and methods of usethereof. More specifically, the present disclosure relates toelectromechanical, hand-held surgical apparatus, devices and/or systemsconfigured for use with removable disposable end effectors and/or singleuse end effectors for clamping, cutting and/or stapling tissue.

2. Background of the Related Art

A number of surgical device manufacturers have developed product lineswith proprietary drive systems for operating and/or manipulatingelectromechanical surgical devices. In many instances theelectromechanical surgical devices include a reusable handle assembly,and disposable or single use end effectors. The end effectors areselectively connected to the handle assembly prior to use and thendisconnected from the handle assembly following use in order to bedisposed of or in some instances sterilized for re-use.

Many of these electromechanical surgical devices include complex drivecomponents that utilize a variety of user interfaces that accept userinputs (e.g., controls) for controlling the devices as well as providefeedback to the user. To prevent actuation of drive mechanisms beyondmechanical limits, various switches and sensors are used to detectoperational state of the surgical devices. Inclusion of multipleswitches and/or sensors in the devices as well as end effectors presentsvarious problems. In addition, cost or other considerations prevent theuse of such devices. Accordingly, there is a need for systems andapparatuses having safety mechanisms that can detect mechanical limitswithout relying on multiple mechanical limit sensors and/or switchesdisposed throughout the surgical device.

SUMMARY

According to one embodiment of the present disclosure a surgicalinstrument is provided. The surgical instrument includes: a handleassembly; a jaw assembly including a staple cartridge containing aplurality of staples and an anvil to form the plurality of staples uponfiring; a drive assembly at least partially located within the handleand connected to the jaw assembly and the lockout mechanism; a motordisposed within the handle assembly and operatively coupled to the driveassembly; and a controller operatively coupled to the motor, thecontroller configured to control supply of electrical current to themotor and to monitor a current draw of the motor, wherein the controlleris further configured to terminate the supply of electrical current tothe motor in response to a rate of change of the current draw indicativeof a mechanical limit of at least one of the jaw assembly, the driveassembly, or the motor.

According to one aspect of the above embodiment, the controller isfurther configured to determine if motor current is unstable bydetermining whether the rate of change of the current draw is outside afirst range.

According to one aspect of the above embodiment, the controller isfurther configured to determine if motor current is stable bydetermining whether the rate of change of the current draw is within asecond range, wherein the second range is within the first range.

According to one aspect of the above embodiment, the controller isfurther configured to store a stability counter of current draw sampleswithin the second range.

According to one aspect of the above embodiment, the controllerdetermines whether motor current is stable if the stability counter isabove a predetermined stability threshold.

According to one aspect of the above embodiment, the controller isfurther configured to determine if the motor reached the mechanicallimit by determining whether the motor current is stable and the rate ofchange of the current draw is within a third range.

According to one aspect of the above embodiment, the third range iswithin the first range and is higher than the second range.

According to one aspect of the above embodiment, the controller isfurther configured to store an event counter of current draw sampleswithin the third range.

According to one aspect of the above embodiment, the controllerdetermines whether the motor reached the mechanical limit if the eventcounter is above a predetermined event threshold.

According to another embodiment of the present disclosure a surgicalinstrument is provided. The surgical instrument includes: a handleassembly; a jaw assembly including a staple cartridge containing aplurality of staples and an anvil to form the plurality of staples uponfiring; a drive assembly at least partially located within the handleand connected to the jaw assembly and the lockout mechanism; a motordisposed within the handle assembly and operatively coupled to the driveassembly; and a controller operatively coupled to the motor, thecontroller to determine whether the motor has reached a mechanical limitbased on a rate of change of a current draw by the motor indicative ofthe mechanical limit.

According to one aspect of the above embodiment, the controller isfurther configured to determine whether motor current is unstable bydetermining whether the rate of change of the current draw is outside afirst range.

According to one aspect of the above embodiment, the controller isfurther configured to determine whether motor current is stable bydetermining whether a plurality of samples of the rate of change of thecurrent draw are within a second range.

According to one aspect of the above embodiment, the controller isfurther configured to store a stability counter of current draw sampleswithin the second range.

According to one aspect of the above embodiment, the controllerdetermines whether motor current is stable if the stability counter isabove a predetermined stability threshold.

According to one aspect of the above embodiment, the controller isfurther configured to determine whether the motor reached the mechanicallimit by determining whether the motor current is stable and a pluralityof samples of the rate of change of the current draw are within a thirdrange.

According to one aspect of the above embodiment, the second and thirdranges are within the first range and the third range is higher than thesecond range.

According to one aspect of the above embodiment, the controller isfurther configured to store an event counter of current draw sampleswithin the third range.

According to one aspect of the above embodiment, the controllerdetermines whether the motor reached the mechanical limit if the eventcounter is above a predetermined event threshold.

According to a further embodiment of the present disclosure a method forcontrolling a surgical instrument is provided. The method includes:monitoring a current draw of a motor coupled to a drive assembly foractuating a jaw assembly; calculating a rate of change of the currentdraw; and determining whether the motor has reached a mechanical limitbased on the rate of change of the current draw by the motor.

According to one aspect of the above embodiment, the method furtherincludes determining whether the rate of change of the current draw isoutside a first range to determine whether motor current is unstable.

According to one aspect of the above embodiment, the method furtherincludes determining whether a plurality of samples of the rate ofchange of the current draw are within a second range to determinewhether motor current is stable.

According to one aspect of the above embodiment, the method furtherincludes: storing a stability counter of current draw samples within thesecond range; and determining whether motor current is stable if thestability counter is above a predetermined stability threshold.

According to one aspect of the above embodiment, the method furtherincludes: whether the motor current is stable and a plurality of samplesof the rate of change of the current draw are within a third range todetermine whether the motor reached the mechanical limit by.

According to one aspect of the above embodiment, the second and thirdranges are within the first range and the third range is higher than thesecond range.

According to one aspect of the above embodiment, the method furtherincludes: storing an event counter of current draw samples within thethird range; and determining whether the motor reached the mechanicallimit if the event counter is above a predetermined event threshold.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are described herein withreference to the accompanying drawings, wherein:

FIG. 1 is a perspective, disassembled view of an electromechanicalsurgical system including a surgical instrument, an adapter, and an endeffector, according to the present disclosure;

FIG. 2 is a perspective view of the surgical instrument of FIG. 1,according to the present disclosure;

FIG. 3 is perspective, exploded view of the surgical instrument of FIG.1, according to the present disclosure;

FIG. 4 is a perspective view of a battery of the surgical instrument ofFIG. 1, according to the present disclosure;

FIG. 5 is a top, partially-disassembled view of the surgical instrumentof FIG. 1, according to the present disclosure;

FIG. 6 is a front, perspective view of the surgical instrument of FIG. 1with the adapter separated therefrom, according to the presentdisclosure;

FIG. 7 is a side, cross-sectional view of the surgical instrument ofFIG. 1, as taken through 7-7 of FIG. 2, according to the presentdisclosure;

FIG. 8 is a top, cross-sectional view of the surgical instrument of FIG.1, as taken through 8-8 of FIG. 2, according to the present disclosure;

FIG. 9 is a perspective, exploded view of a end effector of FIG. 1,according to the present disclosure;

FIG. 10 is a schematic diagram of the surgical instrument of FIG. 1according to the present disclosure;

FIG. 11 is a schematic diagram of motor current values stored in memoryof the surgical instrument of FIG. 1 according to the presentdisclosure;

FIG. 12 is a flow chart of a method for controlling the surgicalinstrument of FIG. 1 according to the present disclosure;

FIGS. 13-15 are plots of motor current of the surgical instrument ascontrolled by the method of the present disclosure; and

FIG. 16 is a flow chart of a method for controlling the surgicalinstrument of FIG. 1 according to another embodiment of the presentdisclosure.

DETAILED DESCRIPTION

A surgical system, in accordance with an embodiment of the presentdisclosure, is generally designated as 10, and is in the form of apowered hand held electromechanical instrument configured for selectiveattachment thereto of a plurality of different end effectors that areeach configured for actuation and manipulation by the powered hand heldelectromechanical surgical instrument.

As illustrated in FIG. 1, surgical instrument 100 is configured forselective connection with an adapter 200, and, in turn, adapter 200 isconfigured for selective connection with an end effector or single useloading unit 300.

As illustrated in FIGS. 1-3, surgical instrument 100 includes a handlehousing 102 having a lower housing portion 104, an intermediate housingportion 106 extending from and/or supported on lower housing portion104, and an upper housing portion 108 extending from and/or supported onintermediate housing portion 106. Intermediate housing portion 106 andupper housing portion 108 are separated into a distal half-section 110 athat is integrally formed with and extending from the lower portion 104,and a proximal half-section 110 b connectable to distal half-section 110a by a plurality of fasteners. When joined, distal and proximalhalf-sections 110 a, 110 b define a handle housing 102 having a cavity102 a therein in which a circuit board 150 and a drive mechanism 160 issituated.

Distal and proximal half-sections 110 a, 110 b are divided along a planethat traverses a longitudinal axis “X” of upper housing portion 108, asseen in FIGS. 2 and 3. Handle housing 102 includes a gasket 112extending completely around a rim of distal half-section and/or proximalhalf-section 110 a, 110 b and being interposed between distalhalf-section 110 a and proximal half-section 110 b. Gasket 112 seals theperimeter of distal half-section 110 a and proximal half-section 110 b.Gasket 112 functions to establish an air-tight seal between distalhalf-section 110 a and proximal half-section 110 b such that circuitboard 150 and drive mechanism 160 are protected from sterilizationand/or cleaning procedures.

In this manner, the cavity 102 a of handle housing 102 is sealed alongthe perimeter of distal half-section 110 a and proximal half-section 110b yet is configured to enable easier, more efficient assembly of circuitboard 150 and a drive mechanism 160 in handle housing 102.

Intermediate housing portion 106 of handle housing 102 provides ahousing in which circuit board 150 is situated. Circuit board 150 isconfigured to control the various operations of surgical instrument 100,as will be set forth in additional detail below.

Lower housing portion 104 of surgical instrument 100 defines an aperture(not shown) formed in an upper surface thereof and which is locatedbeneath or within intermediate housing portion 106. The aperture oflower housing portion 104 provides a passage through which wires 152pass to electrically interconnect electrical components (a battery 156,as illustrated in FIG. 4, a circuit board 154, as illustrated in FIG. 3,etc.) situated in lower housing portion 104 with electrical components(circuit board 150, drive mechanism 160, etc.) situated in intermediatehousing portion 106 and/or upper housing portion 108.

Handle housing 102 includes a gasket 103 disposed within the aperture oflower housing portion 104 (not shown) thereby plugging or sealing theaperture of lower housing portion 104 while allowing wires 152 to passtherethrough. Gasket 103 functions to establish an air-tight sealbetween lower housing portion 106 and intermediate housing portion 108such that circuit board 150 and drive mechanism 160 are protected fromsterilization and/or cleaning procedures.

As shown, lower housing portion 104 of handle housing 102 provides ahousing in which a rechargeable battery 156, is removably situated.Battery 156 is configured to supply power to any of the electricalcomponents of surgical instrument 100. Lower housing portion 104 definesa cavity (not shown) into which battery 156 is inserted. Lower housingportion 104 includes a door 105 pivotally connected thereto for closingcavity of lower housing portion 104 and retaining battery 156 therein.

With reference to FIGS. 3 and 5, distal half-section 110 a of upperhousing portion 108 defines a nose or connecting portion 108 a. A nosecone 114 is supported on nose portion 108 a of upper housing portion108. Nose cone 114 is fabricated from a transparent material. Anillumination member 116 is disposed within nose cone 114 such thatillumination member 116 is visible therethrough. Illumination member 116is may be a light emitting diode printed circuit board (LED PCB).Illumination member 116 is configured to illuminate multiple colors witha specific color pattern being associated with a unique discrete event.

Upper housing portion 108 of handle housing 102 provides a housing inwhich drive mechanism 160 is situated. As illustrated in FIG. 5, drivemechanism 160 is configured to drive shafts and/or gear components inorder to perform the various operations of surgical instrument 100. Inparticular, drive mechanism 160 is configured to drive shafts and/orgear components in order to selectively move tool assembly 304 of endeffector 300 (see FIGS. 1 and 9) relative to proximal body portion 302of end effector 300, to rotate end effector 300 about a longitudinalaxis “X” (see FIG. 2) relative to handle housing 102, to move anvilassembly 306 relative to cartridge assembly 308 of end effector 300,and/or to fire a stapling and cutting cartridge within cartridgeassembly 308 of end effector 300.

The drive mechanism 160 includes a selector gearbox assembly 162 that islocated immediately proximal relative to adapter 200. Proximal to theselector gearbox assembly 162 is a function selection module 163 havinga first motor 164 that functions to selectively move gear elementswithin the selector gearbox assembly 162 into engagement with an inputdrive component 165 having a second motor 166.

As illustrated in FIGS. 1-4, and as mentioned above, distal half-section110 a of upper housing portion 108 defines a connecting portion 108 aconfigured to accept a corresponding drive coupling assembly 210 ofadapter 200.

As illustrated in FIGS. 6-8, connecting portion 108 a of surgicalinstrument 100 has a cylindrical recess 108 b that receives a drivecoupling assembly 210 of adapter 200 when adapter 200 is mated tosurgical instrument 100. Connecting portion 108 a houses three rotatabledrive connectors 118, 120, 122.

When adapter 200 is mated to surgical instrument 100, each of rotatabledrive connectors 118, 120, 122 of surgical instrument 100 couples with acorresponding rotatable connector sleeve 218, 220, 222 of adapter 200 asshown in FIG. 6. In this regard, the interface between correspondingfirst drive connector 118 and first connector sleeve 218, the interfacebetween corresponding second drive connector 120 and second connectorsleeve 220, and the interface between corresponding third driveconnector 122 and third connector sleeve 222 are keyed such thatrotation of each of drive connectors 118, 120, 122 of surgicalinstrument 100 causes a corresponding rotation of the correspondingconnector sleeve 218, 220, 222 of adapter 200.

The mating of drive connectors 118, 120, 122 of surgical instrument 100with connector sleeves 218, 220, 222 of adapter 200 allows rotationalforces to be independently transmitted via each of the three respectiveconnector interfaces. The drive connectors 118, 120, 122 of surgicalinstrument 100 are configured to be independently rotated by drivemechanism 160. In this regard, the function selection module 163 ofdrive mechanism 160 selects which drive connector or connectors 118,120, 122 of surgical instrument 100 is to be driven by the input drivecomponent 165 of drive mechanism 160.

Since each of drive connectors 118, 120, 122 of surgical instrument 100has a keyed and/or substantially non-rotatable interface with respectiveconnector sleeves 218, 220, 222 of adapter 200, when adapter 200 iscoupled to surgical instrument 100, rotational force(s) are selectivelytransferred from drive mechanism 160 of surgical instrument 100 toadapter 200.

The selective rotation of drive connector(s) 118, 120 and/or 122 ofsurgical instrument 100 allows surgical instrument 100 to selectivelyactuate different functions of end effector 300. As will be discussed ingreater detail below, selective and independent rotation of first driveconnector 118 of surgical instrument 100 corresponds to the selectiveand independent opening and closing of tool assembly 304 of end effector300, and driving of a stapling/cutting component of tool assembly 304 ofend effector 300. Also, the selective and independent rotation of seconddrive connector 120 of surgical instrument 100 corresponds to theselective and independent articulation of tool assembly 304 of endeffector 300 transverse to longitudinal axis “X” (see FIG. 2).Additionally, the selective and independent rotation of third driveconnector 122 of surgical instrument 100 corresponds to the selectiveand independent rotation of end effector 300 about longitudinal axis “X”(see FIG. 2) relative to handle housing 102 of surgical instrument 100.

As mentioned above and as illustrated in FIGS. 5 and 8, drive mechanism160 includes a selector gearbox assembly 162; and a function selectionmodule 163, located proximal to the selector gearbox assembly 162, thatfunctions to selectively move gear elements within the selector gearboxassembly 162 into engagement with second motor 166. Thus, drivemechanism 160 selectively drives one of drive connectors 118, 120, 122of surgical instrument 100 at a given time.

As illustrated in FIGS. 1-3, handle housing 102 supports a controlassembly 107 on a distal surface or side of intermediate housing portion108. The control assembly 107 is a fully-functional mechanicalsubassembly that can be assembled and tested separately from the rest ofthe instrument 100 prior to coupling thereto.

Control assembly 107, in cooperation with intermediate housing portion108, supports a pair of finger-actuated control buttons 124, 126 and apair rocker devices 128, 130 within a housing 107 a. The control buttons124, 126 are coupled to extension shafts 125, 127 respectively. Inparticular, control assembly 107 defines an upper aperture 124 a forslidably receiving the extension shaft 125, and a lower aperture 126 afor slidably receiving the extension shaft 127.

Reference may be made to a commonly-owned U.S. patent application Ser.No. 13/331,047, the entire contents of which are incorporated byreference herein, for a detailed discussion of the construction andoperation of the surgical instrument 100.

Referring to FIG. 9, drive assembly 360 of end effector 300 includes aflexible drive shaft 364 having a distal end which is secured to adynamic drive beam 365, and a proximal engagement section 368.Engagement section 368 includes a stepped portion defining a shoulder370. A proximal end of engagement section 368 includes diametricallyopposed inwardly extending fingers 372. Fingers 372 engage a hollowdrive member 374 to fixedly secure drive member 374 to the proximal endof shaft 364. Drive member 374 defines a proximal porthole whichreceives a connection member of drive tube 246 (FIG. 1) of adapter 200when end effector 300 is attached to distal coupling 230 of adapter 200.

When drive assembly 360 is advanced distally within tool assembly 304,an upper beam of drive beam 365 moves within a channel defined betweenanvil plate 312 and anvil cover 310 and a lower beam moves within achannel of the staple cartridge 305 and over the exterior surface ofcarrier 316 to close tool assembly 304 and fire staples therefrom.

Proximal body portion 302 of end effector 300 includes a sheath or outertube 301 enclosing an upper housing portion 301 a and a lower housingportion 301 b. The housing portions 301 a and 301 b enclose anarticulation link 366 having a hooked proximal end 366 a which extendsfrom a proximal end of end effector 300. Hooked proximal end 366 a ofarticulation link 366 engages a coupling hook (not shown) of adapter 200when end effector 300 is secured to distal housing 232 of adapter 200.When drive bar (not shown) of adapter 200 is advanced or retracted asdescribed above, articulation link 366 of end effector 300 is advancedor retracted within end effector 300 to pivot tool assembly 304 inrelation to a distal end of proximal body portion 302.

As illustrated in FIG. 9 above, cartridge assembly 308 of tool assembly304 includes a staple cartridge 305 supportable in carrier 316. Staplecartridge 305 defines a central longitudinal slot 305 a, and threelinear rows of staple retention slots 305 b positioned on each side oflongitudinal slot 305 a. Each of staple retention slots 305 b receives asingle staple 307 and a portion of a staple pusher 309. During operationof instrument 100, drive assembly 360 abuts an actuation sled 350 andpushes actuation sled 350 through cartridge 305. As the actuation sledmoves through cartridge 305, cam wedges of the actuation sled 350sequentially engage staple pushers 309 to move staple pushers 309vertically within staple retention slots 305 b and sequentially eject asingle staple 307 therefrom for formation against anvil plate 312.

The end effector 300 may also include one or more mechanical lockoutmechanisms, such as those described in commonly-owned U.S. Pat. Nos.5,071,052, 5,397,046, 5413,267, 5,415,335, 5,715,988, 5,718,359,6,109,500, the entire contents of all of which are incorporated byreference herein.

Another embodiment of the instrument 100 is shown in FIG. 10. Theinstrument 100 includes the motor 164. The motor 164 may be anyelectrical motor configured to actuate one or more drives (e.g.,rotatable drive connectors 118, 120, 122 of FIG. 6). The motor 164 iscoupled to the battery 156, which may be a DC battery (e.g.,rechargeable lead-based, nickel-based, lithium-ion based, battery etc.),an AC/DC transformer, or any other power source suitable for providingelectrical energy to the motor 164.

The battery 156 and the motor 164 are coupled to a motor driver circuit404 disposed on the circuit board 154 which controls the operation ofthe motor 164 including the flow of electrical energy from the battery156 to the motor 164. The driver circuit 404 includes a plurality ofsensors 408 a, 408 b, . . . 408 n configured to measure operationalstates of the motor 164 and the battery 156. The sensors 408 a-n mayinclude voltage sensors, current sensors, temperature sensors, telemetrysensors, optical sensors, and combinations thereof. The sensors 408a-408 n may measure voltage, current, and other electrical properties ofthe electrical energy supplied by the battery 156. The sensors 408 a-408n may also measure rotational speed as revolutions per minute (RPM),torque, temperature, current draw, and other operational properties ofthe motor 164. RPM may be determined by measuring the rotation of themotor 164. Position of various drive shafts (e.g., rotatable driveconnectors 118, 120, 122 of FIG. 6) may be determined by using variouslinear sensors disposed in or in proximity to the shafts or extrapolatedfrom the RPM measurements. In embodiments, torque may be calculatedbased on the regulated current draw of the motor 164 at a constant RPM.In further embodiments, the driver circuit 404 and/or the controller 406may measure time and process the above-described values as a functionthereof, including integration and/or differentiation, e.g., todetermine the change in the measured values and the like.

The driver circuit 404 is also coupled to a controller 406, which may beany suitable logic control circuit adapted to perform the calculationsand/or operate according to a set of instructions described in furtherdetail below. The controller 406 may include a central processing unitoperably connected to a memory which may include transitory type memory(e.g., RAM) and/or non-transitory type memory (e.g., flash media, diskmedia, etc.). The controller 406 includes a plurality of inputs andoutputs for interfacing with the driver circuit 404. In particular, thecontroller 406 receives measured sensor signals from the driver circuit404 regarding operational status of the motor 164 and the battery 156and, in turn, outputs control signals to the driver circuit 404 tocontrol the operation of the motor 164 based on the sensor readings andspecific algorithm instructions, which are discussed in more detailbelow. The controller 406 is also configured to accept a plurality ofuser inputs from a user interface (e.g., switches, buttons, touchscreen, etc. of the control assembly 107 coupled to the controller 406).

The present disclosure provides for an apparatus and method forcontrolling the instrument 100 or any other powered surgical instrument,including, but not limited to, linear powered staplers, circular orarcuate powered staplers, graspers, electrosurgical sealing forceps,rotary tissue blending devices, and the like. In particular, torque,RPM, position, and acceleration of drive shafts of the instrument 100can be correlated to motor characteristics (e.g., current draw). Currentdrawn by the motor 164 may be used for detecting mechanical limits sincethe current drawn by the motor 164 changes with the load and speed ofthe motor 164. Thus, analysis of the amount of change (e.g., rate ofchange) of current draw allows for distinguishing between differenttypes of load conditions, e.g., load exerted by tissue versus loadexerted by a mechanical stop.

During normal operation of the motor 164 the current draw generally doesnot fall outside a predetermined range (e.g., first range). Duringclamping and stapling, the load exerted on the motor 164 by the tissuevaries within a second range, encompassed by the first range. Inparticular, as the motor 164 encounters an increased load due to thetissue being clamped by the anvil and cartridge assemblies 306, 308 thecurrent draw increases and is within the second range for a secondperiod of time (e.g., increase in the current draw occurs for apredetermined period of time). If the motor 164 encounters a mechanicallimit there is also a corresponding increase in current draw in arelatively short time that is larger than the current draw associatedwith tissue clamping. In particular, the current draw due to amechanical stop is within a third range that is higher than the secondrange for a third period of time. In comparison, startup of the motor164 draws more current than either clamping/fastening or the mechanicalstop and the duration of the increased current draw is the shortest ofthe two current draws described above.

In embodiments, mechanical stops may be detected by comparing motorcurrent with a predetermined threshold since the current drawn by themotor 164 upon encountering a mechanical stop is usually much higherthan the normal operating current. The controller 406 may use thesatisfaction of this condition to shut off the motor 164.

This approach presents some challenges when the motor 164 encountershigh momentary loads during normal operation (e.g., clamping tissue).The current draw associated with tissue clamping can reach thethreshold, thus causing the controller 406 to shut off the motor 164prematurely. In embodiments, the premature shutoff may be prevented byanalyzing normal current draw of the motor 164 and construct a normalmotor load profile. The controller 406 may then be programmed to adjustthe shutoff threshold in accordance with that profile. Thisconfiguration is well-suited to motors 164 having little variation inthe load profile. However, large variations can produce false positivesif the load profile deviates from the current draw associated withnormal use.

Efficiency of the motor 164 and drive mechanism also have an effect incalculating the motor current limit. Since mechanical efficiencies canvary from one instrument to another, each instrument needs to beindividually calibrated during assembly. Further, mechanicalefficiencies change with wear and tear of the instrument and can alsoaffect performance of the software.

The algorithm according to the present disclosure overcomes the issuesof using single-threshold or profile-based algorithms. An advantage ofthe algorithm according to the present disclosure is that the algorithmutilizes rate of change/current over time rather than comparingamplitude of the motor current to a predetermined threshold. The rate ofchange of the motor current associated with different loads, e.g.,normal load, heavy loads, mechanical stops, load spikes, etc. may beclassified into different ranges, in which each range is associated witha specific load. The classification into ranges may then be used toidentify distinct loads on the motor 164 and filtering out spikes causedby starting and stopping of the motor 164. Since the identification ofthe mechanical loads is based on the rate of change in motor currentrather than its amplitude, deviation from the load profiles do notaffect load identification. In addition, mechanical efficiencies do notaffect load identification based on rate of change in motor current.Less efficient instruments draw more current to attain the same speed,however, the slopes (e.g., rate of change in current draw) for reachingthose speeds remains similar to those of more efficient systems. Thiseliminates the need for load profiling and calibration operation duringassembly of the instrument 100.

Another advantage of the algorithm according to the present disclosureis the low computational overhead. The algorithm relies on calculatingthe rate of change of the motor current and as such can be determined bytaking the difference between two values, allowing for implementation ofthe algorithm in an 8-bit microcontroller.

The change in motor current can be measured by sampling currentperiodically. In embodiments, the sampling rate may be from about 100per second to about 10,000 per second, in embodiments from about 500 persecond to about 1,000 per second. The samples may then be used by thecontroller 406 to calculate the change in the motor current (e.g.,current draw). The controller 406 may then use the change in motorcurrent to determine the operating condition of the instrument 100 andtake appropriate action.

The present disclosure also provides a feedback system and method forcontrolling the instrument 100 based on external operating conditionssuch as firing difficulty encountered by the instrument 100 due totissue thickness and/or mechanical stop (e.g., the drive beam 365reaching the distal end of the channel defined in the anvil plate 312and the staple cartridge 305. In addition, the present disclosureprovides for modeling of different usages of the instrument 100 inresponse to the external operating conditions (e.g., specific failures)to derive internal system feedback. The sensor information from thesensors 408 a-n is used by the controller 406 to alter operatingcharacteristics of the instrument 100 and/or notify users of specificoperational conditions. In embodiments, the controller 406 controls(e.g., limits) the current supplied to the motor 164.

The controller 406 includes a computer-readable memory 406 a and/ornon-transitory medium for storing software instructions (e.g.,algorithm) for detecting mechanical limits of the instrument 100 basedon the measured current draw. As used herein, the term “mechanicallimit” denotes any of the electromechanical components reachingend-of-travel positions including, but not limited to, e.g., the drivebeam 365 reaching the distal end of the channel defined in the anvilplate 312 and the staple cartridge 305, actuation of mechanical safetylockout mechanisms preventing travel of the shaft 364, articulation link366 reaching articulation limits of the end effector 300, and the like.

The change in motor current associated with the onset of certain loadconditions (e.g., tissue clamping or mechanical limits) falls withinpredefined ranges and persists for a certain duration. These conditionsare used by the algorithm to identify operating properties of the motor164 and react accordingly in response thereto.

With reference to FIG. 11, the memory 406 a stores a plurality ofcurrent draw values. The memory 406 a includes look-up table 500 or anyother suitable data structure having values “I-V.” The first value I andthe fifth value “V” define a first range encompassing a stable currentdraw signal indicative of normal (e.g., load-bearing) operation of themotor 164. The second and third values “II” and “III” define a secondrange corresponding to the current draw associated with current draw ofthe motor 164 during tissue clamping and fourth and fifth values “IV”and “V” defining a third range corresponding to the current drawassociated with a mechanical stop. In embodiments, the first value “I”may be the same as the second value “II.”

The controller 406 also includes a condition-of-interest counter whichcounts the number of samples during which the slope (e.g., rate ofchange) of the motor current lies within the desired range (e.g., eitherfirst, second or third ranges). The controller 406 also includes asignal stability counter, which counts the number of samples for whichthe slope lies within the second range. The controller 406 determines ifthe measured rate of change current draw signal is stable using thevalues of the table 500. The signal is considered to be unstable if apredetermined number of current draw samples are outside the first rangeand stable if a predetermined number of samples are within the secondrange.

FIG. 12 shows a method according to the present disclosure fordetermining if the motor 164 encounters a mechanical stop. The methodmay be implemented as software instructions (e.g., algorithm) stored inthe controller 406 as described above. Initially, the controller 406calculates a moving average of the measured motor current (e.g., currentdraw). As used herein, the term “moving average” denotes an average of apredetermined subset of samples that is updated every time a new sampleis obtained. The moving average may include from about 2 plurality ofsamples to about 256 plurality of samples, and in embodiments, fromabout plurality of samples 16 about plurality of samples 64, dependingon the sampling rate described above. The controller 406 stores thefirst moving average and calculates the second moving average for thesubsequent sample set. The controller 406 then determines the differencebetween the moving averages to calculate the sample-to-sample change.

As shown in FIGS. 12-13, the moving average of the samples may begraphed as plots 700, 800, 900, with the sample-to-sample change beingrepresented as the slope of the plots 700, 800, 900. The plots 700, 800,900 may be generated and outputted on a display allowing the user toview the current draw of the motor 164. In embodiments, the plots 700,800, 900 may be stored in the memory 406 a as a series of values,without reproducing the sample values as a plot.

The change in the monitored motor current, also defined as the slope isused to differentiate between different types of loads encountered bymotor 164. The controller 406 initially determines if the signal isstable by determining whether the calculated slope/change is outside thefirst range (e.g., the slope is larger than fifth value “V” or less thanfirst value “I”). If the slope lies outside the first range for apredefined number of samples, the controller 406 initializes or resetsthe condition-of-interest and signal stability counters by setting themto zero, 0. In addition, the controller 406 also sets the signal statusas “unstable.”

With reference to FIGS. 14 and 15, the samples below first value “I,” asshown in FIG. 14, and above the fifth value “V,” as shown in FIG. 15,are filtered out since they represent abnormal negative and positivespikes in current draw. These spikes may be caused by starting andstopping of the motor 164 and may result false positives inthreshold-based decision making algorithms.

After determining if the slope is outside the first range, thecontroller 406 determines if the slope is within the second range (valueII≦slope≦value III). If so, the stability counter is incremented. Thecontroller 406 checks if the stability counter has reached apredetermined threshold before changing the signal status to “stable.”This ensures that the sample has been within the second range for asufficient period of time. Any deviation, e.g., the slope being outsidethe first range, resets the condition-of-interest and signal stabilitycounters and sets the signal status as “unstable” as described above.

With reference to FIGS. 13-15, the signal is considered to be stable ifthe slope is within the second range, irrelevant of the actual amplitudeof the motor current samples. Thus, the higher amplitude of the sampleswithin the second range of FIG. 15 and lower amplitude of the sampleswithin the second range of FIGS. 13 and 14 is treated similarly by thealgorithm of the present disclosure as the attribute of interest is therate of change of slope of the motor current samples.

The controller 406 also determines if the sample is within the thirdrange. For each sample within the third range, while the signal isdeemed stable, the condition-of-interest counter is incremented. Everytime the sample falls below second value “II,” the condition-of-interestcounter is decremented. The condition-of-interest counter is used toidentify a mechanical stop, as described in further detail below. If thecondition-of-interest counter is above a predetermined threshold, thenthe controller 406 determines that a mechanical stop has been reached.With reference to FIG. 13, a plurality of samples have a slope thatfalls within the third range, this increments the condition-of-interestcounter and upon reaching the predetermined count triggers theindication that the mechanical stop has been reached. Once thecontroller 406 determines that the mechanical limit has been reached thesupply of current to the motor 164 may be terminated to prevent furtheroperation of the instrument 100 and/or the instrument 100 may issue analarm.

FIG. 16 shows a method according another embodiment of to the presentdisclosure for determining if the motor 164 encounters a mechanicalstop.

The controller 406 includes the stability and condition-of-interestcounters, as described above. The controller 406 further includes apositive spike counter and a negative spike counter. These countersmaintain a number of times a current (e.g., slope) has spiked outsidethe first range. More specifically, the positive spike counter isincremented when the motor current is above the value “V” and thenegative spike counter is incremented when the motor current is belowthe value “I.” The controller 406 determines if the measured rate ofchange current draw signal is stable using the values of the table 500.The signal is considered to be unstable if a predetermined number ofcurrent draw samples are outside the first range (e.g., is the number ofpositive and negative spikes is above a predetermined positive andnegative spike threshold) and stable if a predetermined number ofsamples are within the second range.

The method of FIG. 16 may also be implemented as software instructions(e.g., algorithm) stored in the controller 406 as described above.Initially, the controller 406 calculates a moving average of themeasured motor current (e.g., current draw). As used herein, the term“moving average” denotes an average of a predetermined subset of samplesthat is updated every time a new sample is obtained. The moving averagemay include from about 2 samples to about 256 samples, and inembodiments, from about 16 to about 64 samples, depending on thesampling rate described above. The controller 406 stores the firstmoving average and calculates the second moving average for thesubsequent sample set. The controller 406 then determines the differencebetween the moving averages to calculate the sample-to-sample change(e.g., slope).

The change in the monitored motor current, also defined as the slope, isused to differentiate between different types of loads encountered bymotor 164. The controller 406 initially determines if the slope islarger than fifth value “V” and updated the previous moving average tothe presently calculated moving average. If the slope is above the fifthvalue “V,” the positive spike counter is incremented while the negativespike counter is decremented. In addition, the controller 406 verifiesif the positive spike counter is above a predetermined positive spikecounter threshold. If so, the controller 406 initializes or resets thecondition-of-interest and signal stability counters by setting them tozero, 0. In addition, the controller 406 also sets the signal status as“unstable.” If the positive spike counter is below the predeterminedpositive spike counter threshold, the stability counter is decremented.

After determining if the slope is above the fifth value “V,” thecontroller 406 determines if the sample falls below second value “II,”the condition-of-interest counter is decremented.

The controller 406 also determines if the slope is smaller than thefirst value “I” and updated the previous moving average to the presentlycalculated moving average. If the slope is above the first value “I,”the negative spike counter is incremented while the positive spikecounter is decremented. In addition, the controller 406 verifies if thenegative spike counter is above a predetermined negative spike counterthreshold. If so, the controller 406 initializes or resets thecondition-of-interest and signal stability counters by setting them tozero, 0. In addition, the controller 406 also sets the signal status as“unstable.” If the negative spike counter is below the predeterminednegative spike counter threshold, the stability counter is decremented.

With reference to FIGS. 14 and 15, the samples below first value “I,” asshown in FIG. 14, and above the fifth value “V,” as shown in FIG. 15,are filtered out since they represent abnormal negative and positivespikes in current draw. These spikes may be caused by starting andstopping of the motor 164 and may result false positives inthreshold-based decision making algorithms.

The controller 406 also determines if the slope is within the secondrange (e.g., value “II”≦slope≦value “III”). If so, the stability counteris incremented. The controller 406 also checks if the stability counterhas reached a predetermined threshold before changing the signal statusto “stable.” This ensures that the sample has been within the secondrange for a sufficient period of time. In addition, the controller 406initializes or resets the positive and negative spike counters bysetting them to zero, 0. Regardless whether the stability counter isbelow or above the predetermined threshold, the previous moving averageis updated to the presently calculated moving average. Any deviation,e.g., the slope being outside the first range, also resets thecondition-of-interest and signal stability counters and sets the signalstatus as “unstable” as described above.

The controller 406 also determines if the sample is within the thirdrange. For each sample within the third range, while the signal isdeemed stable, the condition-of-interest counter is incremented. Thecondition-of-interest counter is used to identify a mechanical stop, asdescribed in further detail below. If the condition-of-interest counteris above a predetermined threshold, then the controller 406 determinesthat a mechanical stop has been reached. With reference to FIG. 13, aplurality of samples have a slope that falls within the third range,this increments the condition-of-interest counter and upon reaching thepredetermined count triggers the indication that the mechanical stop hasbeen reached. Once the controller 406 determines that the mechanicallimit has been reached the supply of current to the motor 164 may beterminated to prevent further operation of the instrument 100 and/or theinstrument 100 may issue an alarm.

In addition to basic feedback about device performance the presentdisclosure also provides a method for powered devices to detect anddiscern other external factors, e.g., thicker tissue, which previouslywere difficult to detect. As a result, improved cutoffs and values forlimits can be implemented, greatly improving the safety of powereddevices in use. Using the feedback mechanisms discussed above, users maymake intelligent decisions about what settings and techniques should beused when operating the instrument 100. This intelligence can range fromchoosing a different reload to fire with a linear stapler, deciding tofire at a different articulation angle, to choosing to use a completelydifferent surgical technique.

It should be understood that the foregoing description is onlyillustrative of the present disclosure. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the disclosure. Accordingly, the present disclosure isintended to embrace all such alternatives, modifications and variances.The embodiments described with reference to the attached drawing figuresare presented only to demonstrate certain examples of the disclosure.Other elements, steps, methods and techniques that are insubstantiallydifferent from those described above and/or in the appended claims arealso intended to be within the scope of the disclosure.

What is claimed is:
 1. A surgical instrument, comprising: a handleassembly; a jaw assembly comprising a staple cartridge containing aplurality of staples and an anvil to form the plurality of staples uponfiring; a drive assembly at least partially located within the handleand connected to the jaw assembly and the lockout mechanism; a motordisposed within the handle assembly and operatively coupled to the driveassembly; and a controller operatively coupled to the motor, thecontroller configured to control supply of electrical current to themotor and to monitor a current draw of the motor, wherein the controlleris further configured to terminate the supply of electrical current tothe motor in response to a rate of change of the current draw indicativeof a mechanical limit of at least one of the jaw assembly, the driveassembly, or the motor.
 2. The surgical instrument according to claim 1,wherein the controller is further configured to determine when motorcurrent is unstable by determining whether the rate of change of thecurrent draw is outside a first range of current draw values.
 3. Thesurgical instrument according to claim 2, wherein the controller isfurther configured to determine if motor current is stable bydetermining whether the rate of change of the current draw is within asecond range of current draw values, wherein the second range is withinthe first range.
 4. The surgical instrument according to claim 3,wherein the controller is further configured to store a stabilitycounter of current draw samples within the second range.
 5. The surgicalinstrument according to claim 4, wherein the controller determineswhether motor current is stable when the stability counter is above apredetermined stability threshold.
 6. The surgical instrument accordingto claim 5, wherein the controller is further configured to determinewhen the motor has reached the mechanical limit by determining whetherthe motor current is stable and the rate of change of the current drawis within a third range.
 7. The surgical instrument according to claim6, wherein the third range is within the first range and is higher thanthe second range.
 8. The surgical instrument according to claim 6,wherein the controller is further configured to store an event counterof current draw samples within the third range.
 9. The surgicalinstrument according to claim 8, wherein the controller determineswhether the motor has reached the mechanical limit when the eventcounter is above a predetermined event threshold.
 10. A surgicalinstrument, comprising: a handle assembly; a jaw assembly comprising astaple cartridge containing a plurality of staples and an anvil to formthe plurality of staples upon firing; a drive assembly at leastpartially located within the handle and connected to the jaw assemblyand the lockout mechanism; a motor disposed within the handle assemblyand operatively coupled to the drive assembly; and a controlleroperatively coupled to the motor, the controller configured to determinewhether the motor has reached a mechanical limit based on a rate ofchange of a current draw by the motor indicative of the mechanicallimit.
 11. The surgical instrument according to claim 10, wherein thecontroller is further configured to determine whether motor current isunstable by determining whether the rate of change of the current drawis outside a first range.
 12. The surgical instrument according to claim11, wherein the controller is further configured to determine whethermotor current is stable by determining whether a plurality of samples ofthe rate of change of the current draw are within a second range. 13.The surgical instrument according to claim 12, wherein the controller isfurther configured to store a stability counter of current draw sampleswithin the second range.
 14. The surgical instrument according to claim13, wherein the controller determines whether motor current is stablewhen the stability counter is above a predetermined stability threshold.15. The surgical instrument according to claim 12, wherein thecontroller is further configured to determine whether the motor reachedthe mechanical limit by determining whether the motor current is stableand a plurality of samples of the rate of change of the current draw arewithin a third range.
 16. The surgical instrument according to claim 15,wherein the second and third ranges are within the first range and thethird range is higher than the second range.
 17. The surgical instrumentaccording to claim 15, wherein the controller is further configured tostore an event counter of current draw samples within the third range.18. The surgical instrument according to claim 17, wherein thecontroller determines whether the motor has reached the mechanical limitwhen the event counter is above a predetermined event threshold.